Pricing via Processing or Combating Junk Mail
Paper of what will later become <<<PoW>>> (Proof of work) on Blockchain environments
We present a computational technique for combatting junk mail, in particular, and controlling access to a shared resource, in general. The main idea is to require a user to compute a moderately hard, but not intractable, function in order to gain access to the resource, thus preventing frivolous use.
It also introduces the concept of a "trap door" (not found on later PoW mechanisms)
The pricing function may be chosen to have something like a _trap door_: given some additional information the computation would be considerably less expensive. We call this a /shortcut/. The shortcut may be used by the resource manager to allocate cheap access to the resource, as the manager sees fit, by bypassing the control mechanism. For example, in the case of electronic mail the shortcut permits the post office to grant bulk mailings at a price chosen by the post office, circumventing the cost of directly evaluating the pricing function for each recipient.